Control of electrical to thermal conductivity ratio for <i>p</i>-type La_xFe₃CoSb₁₂ thermoelectrics by using a melt-spinning process

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>In this work we improved the thermoelectric figure of merit <I>ZT</I> in a La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> (x = 0.80, 0.85, 0.90) skutterudite system by applying a conductivity ratio (electrical to thermal) control method based on the phonon-glass electron-crystal (PGEC) approach. Polycrystalline bulks of La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> were prepared by melt-spinning and subsequent spark plasma sintering. Based on the thermoelectric transport properties and microstructural analysis, we found that large amount of La-filler (x ≥ 0.9) in the La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> system is necessary to increase the conductivity ratio required to improve the thermoelectric properties in the La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> system. Resultantly, the maximum <I>ZT</I> value of 0.87 was obtained at 723 K in the heavily filled La<SUB>0.9</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB>. We discuss our results on the basis of the filling level dependence of the rattling effect and on the formation of the skutterudite single phase. We also confirm that a large amount of La-filling level is necessary to meet the electrical neutrality condition of the <I>p</I>-type La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> skutterudite system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanocrystalline of La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> samples were prepared by melt-spinning and SPS sintering. </LI> <LI> The conductivity ratio is a critical parameter to determine thermoelectric performance. </LI> <LI> Large amount of La filler is necessary to increase the conductivity ratio. </LI> <LI> Rattling effect by La filler is confirmed to be the main mechanism for phonon scattering. </LI> </UL> </P>